Example: Race LA+2, Race LA+2, HD 4 << This is a playable combo. You have +4 LA total from the two races and can sell your 4 HD for another +2 LA. You now have a +6LA character with 1 class level.
Another valid Example: Race +1LA, Race +1LA << Playable combo. You could spend your residual +4 LA on class levels leaving you with a +2LA, 5th level character.
Essentially you get +6LA to mess around with. Pick and choose from what you want just make sure the ends result leaves you with +6LA or +LA whatever with class levels.